Re-evaluating low-carbohydrate diets and mortality
Authors: Richard D Feinman, Katharina Lechner, Eugene J Fine, Jennifer Elliott, Maeve Thompson-Starkey, L Amber O’Hearn, Nicolai Worm
Journal: The Lancet Public Health (2022)

In the area of public health, there is little agreement on the dietary principles for the prevention and treatment of disease. Discussion is highly controversial; in particular for diets based on carbohydrate restriction. In their Article,1Seidelmann SB Claggett B Cheng S et al.Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis.Lancet Public Health. 2018; 3: 419-428Summary Full Text Full Text PDF PubMed Scopus (305) Google Scholar Sara B Seidelmann and colleagues concluded that low-carbohydrate diets were associated with increased all-cause mortality. Here we re-evaluate their work from the standpoint of traditional and novel criteria, potential effect on public awareness, and the practice of nutritional medicine. First, in terms of relevance and accuracy, Seidelmann and colleagues did not investigate a low-carbohydrate diet as a specific intervention, contrary to the general understanding and expectation of patients and health-care providers. Instead, carbohydrate consumption was evaluated using data from the Atherosclerosis Risk in Communities (ARIC) study,2The ARIC investigatorsThe Atherosclerosis Risk in Communities (ARIC) study: design and objectives.Am J Epidemiol. 1989; 129: 687-702Crossref PubMed Scopus (2799) Google Scholar which was not designed for this purpose. Of note, Seidelmann and colleagues relied on semi-quantitative food frequency questionnaires that have been criticised for high error rates.3Archer E Marlow ML Lavie CJ Controversy and debate: Memory-Based Methods Paper 1: the fatal flaws of food frequency questionnaires and other memory-based dietary assessment methods.J Clin Epidemiol. 2018; 104: 113-124Summary Full Text Full Text PDF PubMed Scopus (54) Google Scholar Data were collected twice per patient with a 6-year interval. Furthermore, the benefits of therapeutic carbohydrate restriction4Feinman RD Pogozelski WK Astrup A et al.Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base.Nutrition. 2015; 31: 1-13Crossref PubMed Scopus (440) Google Scholar, 5Hyde P Sapper T Crabtree C et al.Dietary carbohydrate restriction improves metabolic syndrome independent of weight loss.JCI Insight. 2019; 4e128308Crossref PubMed Scopus (81) Google Scholar, 6Athinarayanan SJ Adams RN Hallberg SJ et al.Long-term effects of a novel continuous remote care intervention including nutritional ketosis for the management of type 2 diabetes: a 2-year non-randomized clinical trial.Front Endocrinol. 2019; 10: 348Crossref PubMed Scopus (113) Google Scholar were not discussed in the Article. Strength of association is generally taken to be the most important criterion when considering causality in nutritional epidemiology. In the Article,1Seidelmann SB Claggett B Cheng S et al.Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis.Lancet Public Health. 2018; 3: 419-428Summary Full Text Full Text PDF PubMed Scopus (305) Google Scholar the hazard ratio for the lowest carbohydrate intake quintile compared with a moderate carbohydrate intake was 1·2, which is very close to 50:50 odds. In multivariable analyses, low-carbohydrate diets in various forms have provided overwhelming benefit in treating obesity, diabetes, and metabolic syndrome,4Feinman RD Pogozelski WK Astrup A et al.Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base.Nutrition. 2015; 31: 1-13Crossref PubMed Scopus (440) Google Scholar, 5Hyde P Sapper T Crabtree C et al.Dietary carbohydrate restriction improves metabolic syndrome independent of weight loss.JCI Insight. 2019; 4e128308Crossref PubMed Scopus (81) Google Scholar, 6Athinarayanan SJ Adams RN Hallberg SJ et al.Long-term effects of a novel continuous remote care intervention including nutritional ketosis for the management of type 2 diabetes: a 2-year non-randomized clinical trial.Front Endocrinol. 2019; 10: 348Crossref PubMed Scopus (113) Google Scholar which predicts a reduction in all-cause mortality, whereas the Article suggested an increase.1Seidelmann SB Claggett B Cheng S et al.Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis.Lancet Public Health. 2018; 3: 419-428Summary Full Text Full Text PDF PubMed Scopus (305) Google Scholar Seidelmann and colleagues did not indicate what other factors are presumed to override such a reduction, or include any numerical calculations to show the relative contributions of different factors. In summary, no low-carbohydrate diet was tested in the ARIC study.2The ARIC investigatorsThe Atherosclerosis Risk in Communities (ARIC) study: design and objectives.Am J Epidemiol. 1989; 129: 687-702Crossref PubMed Scopus (2799) Google Scholar As such, we believe that Seidelmann and colleagues' study1Seidelmann SB Claggett B Cheng S et al.Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis.Lancet Public Health. 2018; 3: 419-428Summary Full Text Full Text PDF PubMed Scopus (305) Google Scholar conclusions, if taken as a basis for recommendations, might be a risk in restricting patient choices, inhibiting future research, and impeding the advancement of public health. We declare no competing interests. Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysisBoth high and low percentages of carbohydrate diets were associated with increased mortality, with minimal risk observed at 50–55% carbohydrate intake. Low carbohydrate dietary patterns favouring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality, whereas those that favoured plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain breads, were associated with lower mortality, suggesting that the source of food notably modifies the association between carbohydrate intake and mortality. Full-Text PDF Open Access